Protection of electrical apparatus



March 17, 1931.

M. BUCHHOLZ PROTECTION OF ELECTRICAL APPARATUS Filed 061;. 29, 1927 Inventor: M x Buchholz Patented Mar. 17,1931

UNITED STATES MAX BUCKHOLZ, OF CASSEL, GERMANY PROTECTION OF ELECTRICAL APPARATUS Application filed October 29, 1927, Serial No. 229,691, and in Germany November 2, 1928.

M invention refers to the protection of insu ated electrical apparatus of all kinds, such as transformers, choke coils, switches, motors, dynamos, and so on, gainst damage and possible destruction arising from the accumulation and ignition of gases and vapors of decomposition generated b the insulation. It is a well known fact t at in the case of disturbances in the operation of electrical 1o apparatus of the kind aforesaid, or in the caseof sparkin or other irregularities of operation, or w enever such irregularities are imminent, gases or vapors will be generated by the decomposition of the solid or liquid insulating medium surroundin all or part of the apparatus in question. in Letters Patent of the United States Nos. 1,642,397, 1,642,398, etc, I have shown means for protecting such apparatus, which are operated by such products of decomposition and are combined with an optical or acoustic alarm, or a cut-out or the like, and on being set operating by gases of decomposition of the kind aforesaid will operate such alarm, cut-out or other protective device.

To a certain extent the present invention is an improvement upon the methods and means disclosed in my former patents. According to the present invention the gases or vapors of decom osition of the insulating material are caused to pass by diffusion into a space or chamber separated from the apparatus to be protected and to create in such space or chamber a variation of physical conditions, such as pressure or temperature, wherebythe operative condition of suitable protective means, such as for instance an electrical circuit including an alarm or out out is closed. In such manner I may for instance effect a rise or drop of pressure in the space to the rear of the porous wall, which may not only operate an alarm or cut-out, but may as well stop the excitation of the dynamo, open the valves of a battery or of a container filled with an inert gas or the like adapted to stifle combustion, etc.

In the drawings aflixed to this specification and forming part thereof a number of arrangements illustrating my invention are shown diagrammatically by way of example.

Fig. l is a vertical section of a transformer I casing, illustratin the invention and Fig. 2 is a simi ar view, in which a compensating vessel is mounted on the transormer casing and in communication therewith. Fig. 3 is a diagrammatic section of an air cooled electrical apparatus, such as a motor or generator with a ries therewith.

porous cell arranged in se- Fig. 4 is a similar view illustrating a porous cell arranged in the cooling circulation of a generator. 7

Fig. 5 illustrates a part of a cell formed of a mixture of cell material with catalytically active material. 4 I

Fig. 6 illustrates a cell in which catalytically active material is arranged, while r Fig. 7 shows a cell with catalytically active material arranged on the outer surface. Referring first to Fig. 1, a is a vessel filled partly with oil or some other insulatin medium surrounding a transformer, switc or the like. In the cover of this vessel isarranged a cell 6 made of clay or some other porous material. A tube 11' communicatin with the interior of the cell is bent twice an partly filled with'mercury covering one terminal c of a protective circuit, while the other terminal is divided into two contacts (1 d one in each ascending branch of the mercury tube.

ture of the gas mixture in the clay cell is the same as that in the space. above the insulating liquid in the vessel a, their pressure will remain the same and the branches of mercury will be on equal levels, the circuit being open. However as soon as gases of decomposition, such as for instance hydrogen, methane, ethylen, acetylen, are formed, these gases, on coming in contact with the walls of the cell, will migrate across the porous walls by diffusion and will now cause a rise or reduction of pressure in the cell, which will act on the mercury in tube 03, displacing same in such As long as the composition and temperamanner as to close the circuit either at con- The mercury contact may obviously be replaced by some other electrical contact device, for instance a diaphragm contact or the like such as shown for instance in Fig. 3, and the electrical contact arrangement as a Whole may be replaced by a mechanical device, such as a pawl, etc.

In the modification illustrated in Fig. 2, e is a porous disc consisting of plaster oi Paris, clay or the like, which is arranged in the cover of the compensating vessel or of the transformer. Above the disc 6 the opening of the cover is closed by a diaphragm 9 adapted, upon expansion, to close a protective circuit. T he space 7' between disc 6 and diaphragm 5 here corresponds to the interior of the cell Z) in Fig. l, and the action of gases of decomposition rising in the liquid in the compensating tank and entering the space 7 by diffusion will be substantially the same.

In Fig. 3, it is an electrical apparatus, for instance a motor or generator, and i is a casing surrounding same. The apparatus h is being cooled by a current of air traversing the casing i in the direction of the arrows. To the rear of the apparatus in the direction of the air currentis arranged the cell 6 having the form of a diaphragm enclosed between porous walls and capable, when actuated, to close a protective circuit. /Vhenever the circulating cooling liquid contains some foreign gas, which may have formed by decomposition of the material enclosed in the apparatus, for instance hydrogen, methan, carbon monoxide, carbon dioxide or the like, there will arise in correspondence with the phy ical law or" dillusion a pressure above or below normal Within the porous cell, which known under the denomination osmotic pressure, and which can be utilized for actuating an electric contact of any desired form, for instance a mercury contact, a diaphragm contact or the like, whereby a protective circuit is closed or opened.

Fig. 4 illustrates a porous eeil. Z7 arranged in the cooling gas circulation ot a generator. 7.: is the generator, Z is the cooler, m are the conduits connecting same and torn the cooling air circulation. at is a branch conduit inserted in the circulation and 7) is a porous cell arranged in n. The conduit n is permanently traversed by part of the cooling current, the velocity of which may be adjusted by means of a stopper 0. Whenever a. decomposition of insulating material occurs on the generator, the gases of decomposition will be carried along by thecooiing gas and on reaching the cell 5 will enter same by diltusion and will actuate the protective device as before described.

instead of air g branch conduit a, it may also be arranged in a branch conduit p.

in order to prevent the pores of the cell the cell I) in the.

walls from getting clogged by dust orv the like, the cell is preferably enclosed in an envelope formed of silk gauze, asbestos, glass wool, or the like.

In order that the cell, after gas of decomposition has entered it, be rendered available for further service as quickly as possible, I may arrange for an intermittent ventilating of the cell, for instance by providing apertures in the bottom cover of the cell with valves arranged therein which are positively controlled for instance from the shaft of the motor or generator. \Vhen the valves are opened, the pressure is equalized and in order to expedite such equalization an air current or the like may be passed through the cell, whereupon the valves will close automatically, the cell being thus rendered operative again.

By intermittently opening the cell I further obtain that the contact device is not set operating by some variations of temperature and pressure of the surrounding atmosphere.

The introduction of an air current into the cell involves the further advantage that it the air should be charged with gases only very slowly, so that the percentage of gas inside and outside of the cell will gradually become the same without any variation of pressure capable of operating the protective device arising in the cell, the operation of the cell is nevertheless guaranteed as soon as the percentage of gas becomes great enough.

The effect of variations of pressure in the cell can be increased by combining the cell with a substance capable of exerting a catalytical effect on the gases entering the cell, this effect being a physical or a chemical one.

As shown in Fig. 5, catalytically active material H may be admixed to the material forming the cell wall, while in Fig. 6 I have shown such catalytically active material G to be arranged within the cell, Fig. 7 showing the arrangement of such material on the outsidr f the cell.

1 ay for instance use palladium as a physically active catalyst'or platinum as a chemically active catalyst, both these subnccs lr ng capable of. generating heat en in contact with the gases of decomposition, such heat being utilized for heating the air or other gas in the cell, thereby increasing the variations of pressure.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

I claim l. The method of controlling conditions of insulated electrical which comprises exposing accll, the wall of which is of that character of porosity which will permit osmotic dillusion ot the products of decomposition. occurring in the insulation of the apparatus due to abnormal conditions.

abnormal apparatus 1 to take place therethrough, and causing the variation in physical conditions within the cell due to osmotic action of the products of decomposition to vary the operative condition of protective means associated with said apparatus.

2. The method of controlling abnormal conditions of insulated electrical apparatus Ill fit)

which comprises exposing a cell, the wall of which is of that character of porosity which will permit osmotic diffusion of the products of decomposition, occurring in the insulation of the apparatus due to abnormal conditions, to take place therethrough, and causing the variation in physical conditions within the cell due to osmotic action of the products of decomposition to vary the operative condition of a protective circuit associated with said apparatus.

3. The method of controlling abnormal conditions of insulated electrical apparatus which comprises directing the products of decomposition, occurring in the insulation of said apparatus due to abnormal conditions, about a cell, the wall of which is of that character of porosity which will permit osmotic diffusion to take place, and operating a protective circuit by the osmotic pressure produced in the cell due to the osmotic action of the products of decomposition.

4. Protective system for insulated electricai apparatus comprising the apparatus to be protected, insulating material in contact with said apparatus, a porous wall forming part of a chamber and having the property of permitting osmotic difi'usion of gases therethrough and protective means adapted to be influenced by a variation of hysical conditions in such chamber produced by diffusion of gases of decomposition in the apparatus through the porous wall aforesaid.

5. Protective system for insulated electrical apparatus comprising the apparatus to be protected, insulating material in contact with said apparatus, a porous wall forming part of a chamber and having the property of permitting osmotic diffusion of gases therethrough and protective means adapted to be influenced by a variation of pressure in such chamber produced by ditfuslon of gases of decomposition in the apparatus through the porous wall aforesaid.

-6. Protective system for insulated electrical apparatus comprising the apparatus to be protected, insulating material in contact with said apparatus, a 'cell having porous walls and having the property of permitting osmotic diffusion of gases'therethrough and protective means adapted to be influenced b a variation of physical conditions in such cell produced by diffusion of gases of decomposition in the apparatus through theporous wall aforesaid Y. Protective system for insulated electrical apparatus comprising the apparatus to be protected, insulating material in contact with said apparatus, a cell having porous walls which will permit osmotic diffusion to take place therethrough, said cell being arranged so as to be exposed to the gases of said apparatus, catalyticall active material associated with said cell an protective means adapted to be influenced by a variation of physical conditions in such cell.

8. Protective system for insulated electrical apparatus comprising the apparatus to be protected, insulating material in-contact with said apparatus, a cyclic conduit for cooling means associated with said apparatus, a porous wall in said conduit having the property of permitting osmotic diffusion of gases therethrough and protective means adapted to be infiuencedby variations of physical conditions to the rear of such wall in consequence of the passage therethrough of such gases.

9. Protective system for insulated electrical apparatus comprising the apparatus to be protected, insulating material in contact with said apparatus, a cyclic conduit for cooling means associated with said apparatus, a branch conduit forming part of said cyclic conduit, a porous wall in said branch conduit having the property of permitting osmotic diffusion of gases therethrough and protective means adapted to be influenced by variations of physical conditions to the rear of such wall in consequence of the passage therethrough of such gases.

In testimony whereof I afiix my signature.

MAX BUCHHOLZ. 

